/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.io.range;



import com.google.protobuf.ByteString;

import com.google.protobuf.ByteString.ByteIterator;



import javax.annotation.Nonnull;

import java.io.Serializable;

import java.nio.ByteBuffer;



import static com.bff.gaia.unified.vendor.guava.com.google.common.base.Preconditions.checkNotNull;



/**

 * A class representing a key consisting of an array of bytes. Arbitrary-length {@code byte[]} keys

 * are typical in key-value stores such as Google Cloud Bigtable.

 *

 * <p>Instances of {@link ByteKey} are immutable.

 *

 * <p>{@link ByteKey} implements {@link Comparable Comparable&lt;ByteKey&gt;} by comparing the

 * arrays in lexicographic order. The smallest {@link ByteKey} is a zero-length array; the successor

 * to a key is the same key with an additional 0 byte appended; and keys have unbounded size.

 *

 * <p>Note that the empty {@link ByteKey} compares smaller than all other keys, but some systems

 * have the semantic that when an empty {@link ByteKey} is used as an upper bound, it represents the

 * largest possible key. In these cases, implementors should use {@link #isEmpty} to test whether an

 * upper bound key is empty.

 */

public final class ByteKey implements Comparable<ByteKey>, Serializable {

  /** An empty key. */

  public static final ByteKey EMPTY = ByteKey.of();



  /**

   * Creates a new {@link ByteKey} backed by a copy of the data remaining in the specified {@link

   * ByteBuffer}.

   */

  public static ByteKey copyFrom(ByteBuffer value) {

    return new ByteKey(ByteString.copyFrom(value));

  }



  /**

   * Creates a new {@link ByteKey} backed by a copy of the specified {@code byte[]}.

   *

   * <p>Makes a copy of the underlying array.

   */

  public static ByteKey copyFrom(byte[] bytes) {

    return new ByteKey(ByteString.copyFrom(bytes));

  }



  /**

   * Creates a new {@link ByteKey} backed by a copy of the specified {@code int[]}. This method is

   * primarily used as a convenience to create a {@link ByteKey} in code without casting down to

   * signed Java {@link Byte bytes}:

   *

   * <pre>{@code

   * ByteKey key = ByteKey.of(0xde, 0xad, 0xbe, 0xef);

   * }</pre>

   *

   * <p>Makes a copy of the input.

   */

  public static ByteKey of(int... bytes) {

    byte[] ret = new byte[bytes.length];

    for (int i = 0; i < bytes.length; ++i) {

      ret[i] = (byte) (bytes[i] & 0xff);

    }

    return ByteKey.copyFrom(ret);

  }



  /** Returns a read-only {@link ByteBuffer} representing this {@link ByteKey}. */

  public ByteBuffer getValue() {

    return value.asReadOnlyByteBuffer();

  }



  /**

   * Returns a newly-allocated {@code byte[]} representing this {@link ByteKey}.

   *

   * <p>Copies the underlying {@code byte[]}.

   */

  public byte[] getBytes() {

    return value.toByteArray();

  }



  /** Returns {@code true} if the {@code byte[]} backing this {@link ByteKey} is of length 0. */

  public boolean isEmpty() {

    return value.isEmpty();

  }



  /**

   * {@link ByteKey} implements {@link Comparable Comparable&lt;ByteKey&gt;} by comparing the arrays

   * in lexicographic order. The smallest {@link ByteKey} is a zero-length array; the successor to a

   * key is the same key with an additional 0 byte appended; and keys have unbounded size.

   */

  @Override

  public int compareTo(@Nonnull ByteKey other) {

    checkNotNull(other, "other");

    ByteIterator thisIt = value.iterator();

    ByteIterator otherIt = other.value.iterator();

    while (thisIt.hasNext() && otherIt.hasNext()) {

      // (byte & 0xff) converts [-128,127] bytes to [0,255] ints.

      int cmp = (thisIt.nextByte() & 0xff) - (otherIt.nextByte() & 0xff);

      if (cmp != 0) {

        return cmp;

      }

    }

    // If we get here, the prefix of both arrays is equal up to the shorter array. The array with

    // more bytes is larger.

    return value.size() - other.value.size();

  }



  ////////////////////////////////////////////////////////////////////////////////////

  private final ByteString value;



  private ByteKey(ByteString value) {

    this.value = value;

  }



  /** Array used as a helper in {@link #toString}. */

  private static final char[] HEX =

      new char[] {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};



  // Prints the key as a string "[deadbeef]".

  @Override

  public String toString() {

    char[] encoded = new char[2 * value.size() + 2];

    encoded[0] = '[';

    int cnt = 1;

    ByteIterator iterator = value.iterator();

    while (iterator.hasNext()) {

      byte b = iterator.nextByte();

      encoded[cnt] = HEX[(b & 0xF0) >>> 4];

      ++cnt;

      encoded[cnt] = HEX[b & 0xF];

      ++cnt;

    }

    encoded[cnt] = ']';

    return new String(encoded);

  }



  @Override

  public boolean equals(Object o) {

    if (o == this) {

      return true;

    }

    if (!(o instanceof ByteKey)) {

      return false;

    }

    ByteKey other = (ByteKey) o;

    return (other.value.size() == value.size()) && this.compareTo(other) == 0;

  }



  @Override

  public int hashCode() {

    return value.hashCode();

  }

}